1. Field of the Invention
The present invention relates to a method of processing hot dross of aluminum resulting from an aluminum smelting process. The present invention relates also to a deoxidant for use in deoxidizing process of oxidation smelting of steel.
2. Description of Related Art
Conventionally, hot dross of aluminum resulting from an aluminum smelting process has been treated as follows to recover aluminum contents therein. First, hot dross of aluminum is scraped out from a smelting-furnace of aluminum and filled into a container. Then, the hot dross of aluminum filled in the container is added with a large amount of flux so that the hot dross of aluminum reacts with flax to oxidize. With this oxidation, the hot dross of aluminum is heated to about 850 degrees of Centigrade in order that rigid, high protective oxide layers (.gamma.-Al.sub.2 O.sub.3 spinel-type cubic system) covering the aluminum droplets residing in the hot dross are transformed to low protective oxide layers (.alpha.-Al.sub.2 O.sub.3, hexagonal system).
Thereafter, the hot dross of aluminum is subject to mechanical stirring so that molten aluminum residing in the hot dross in the form of droplets covered with the low protective oxide layer is removed the oxide layer therefrom and divided from the removed low protective oxide layer. At the same time, during the mechanical stirring process, the aluminum droplets become those of larger size and descend toward the bottom of the container. After the aluminum droplets gathered on the bottom of the container are recovered from the container, the dross residues in the powder state are cooled by a water-cooling drum and abandoned as an industrial waste.
The conventional method of processing the hot dross of aluminum has several defects. First, since a large amount of flux is used to recover the aluminum content residing in the hot dross, there gives rise to problems that dusts containing a large amount of chloride are generated and that a large amount of heat is generated in an explosive manner. These may cause the environmental disruption.
Second, the hot dross after the aluminum content is removed therefrom is in a state heated to a temperature exceeding 1200 degrees of Centigrade, and therefore it must be cooled rapidly so as to suppress reaction of aluminum content thereof with oxygen and nitrogen. However, rapid cooling cannot be carried out with the conventional water-cooling drum. In addition, explosive evaporation of water may occur when the hot dross is subject to a cooling water. Further, since the hot dross after the aluminum content is removed is in a powder state and so has a large amount of surface area, where the hot dross is cooled for a long period of time in the atmosphere, metal aluminum residing in the hot dross reacts with oxygen and nitrogen. This causes to prevent the remaining metal aluminum in the dross from effective reuse. Furthermore, since the dross after cooling process contains more than 10 weight percents of nittided aluminum, it must be reacted with water to transform the nittided aluminum into ammonia gas and aluminum hydroxide before disposal as an industrial waste. However, since the reaction rate of the nitride aluminum and water is extremely low, this process is not applicable industrially.
Third, since the hot dross after the molten aluminum is removed is in a powder state, a large amount of dust may be generated during cooling operation in which the cooling drum is rotated to cool the powders of hot dross. Thus, it is necessary to collect the generated dust by a dust collector.
Accordingly, an object of the present invention is to provide a method of processing hot dross resulting from an aluminum smelting process, which does not emit dust or explosive heat during the process to cause the environmental disruption.
The other object of the present invention is to provide a method of processing hot dross resulting from an aluminum smelting process, which effectively removes air contained in the hot dross to thereby prevent aluminum content remaining in the hot dross from reacting with oxygen or nitrogen.
Another object of the present invention is to provide a deoxidizing solid aluminum dross resulting from a method according to the present invention, which is utilized in deoxidizing process of molten steel.